Comparison of cytochrome P450IA1 induction with the chemical composition of fly ash from combustion of chlorine containing material

Abstract

Polychlorinated dibenzo- p -dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are ubiquitous in the environment. Combustion of organic material, particularly in the presence of chlorine, is a significant source of these harmful compounds. In this study, the induction of cytochrome P450IA1 - measured as aryl hydrocarbon hydroxylase and 7-ethoxyresorufin O-deethylase activities - in the mouse hepatoma cell line, Hepa-1, was used as a biological indicator of the presence of PCDDs and PCDFs in fly ash collected from combustion of chlorine containing material. The highest chlorine content in the combustions studied was 1.2 % (w/w) in a mixture of coal and bark. An amount corresponding to about 7.0 mg of the respective fly ash per ml of growth medium was enough to elicit a half-maximal (ED50) induction of cytochrome P450IA1 in Hepa-1 cells. The inducing compounds were located in the fly ash fraction which contained the PCDDs and PCDFs. There was a good correlation between the PCDD/PCDF composition of the fly ashes and the enzyme inducing effect they had.